How long does it take a 750W heater to raise the temperature of 1kg of water from 20oC to 50oC [specific heat capacity of water = 4200Jkg-1K-1]

Answer Details

To calculate the time it takes for a 750W heater to raise the temperature of 1kg of water from 20°C to 50°C, we can use the formula:
Q = mcΔT
where Q is the heat energy required to heat up the water, m is the mass of water, c is the specific heat capacity of water, and ΔT is the change in temperature.
Solving for Q, we get:
Q = mcΔT
Q = 1kg x 4200J/kg°C x (50°C - 20°C)
Q = 126000J
Now, we can use the formula for power to find out how long it takes for the heater to produce 126000J of heat energy:
P = E/t
t = E/P
where P is the power of the heater, E is the energy produced by the heater, and t is the time taken.
Solving for t, we get:
t = E/P
t = 126000J / 750W
t = 168 seconds
Therefore, the answer is 168s.